The wireless sensor network has been ever increasingly applied with its evolution. The most common scenario of the wireless sensor network is a data monitoring and acquisition system, which transmits the acquired data to a data processing server for summarizing, processing and etc. Generally, the data monitoring and acquisition system supports two kinds of modes, i.e. the remote data acquisition mode and the short-distance data acquisition mode. The remote data acquisition is a communication between a wireless sensor in charge of corresponding data acquisition and a remote data acquisitor, the acquired data is transmitted to a data acquisitor, and then transmitted to the data processing server via the data acquisitor. The short-distance data acquisition is a communication between a wireless sensor in charge of corresponding data acquisition and a short-distance hand-held mobile terminal, the acquired data is transmitted to the data processing server via the mobile terminal.
Power consumption is a main challenge faced by the data monitoring and acquisition system based on the wireless sensor network. Because most of the wireless sensors adopt battery charging, and it is unlikely to charge or, change the battery frequently, the wireless sensor generally uses the operation mode of “monitoring+sleeping” to reduce the power consumption, and during the data acquisition, the wireless sensor is woken up by the data acquisitor or the mobile terminal. The common monitoring-sleeping method includes a time-synchronous monitoring-sleeping method and a time-asynchronous monitoring-sleeping method. The time-synchronous monitoring-sleeping method makes use of the periodical characteristics of the data monitoring and acquisition task. Firstly, a strict time synchronization is performed between all the wireless sensors and the data acquisitor/mobile terminal; then, the wireless sensor is woken up at a preset time period to read the data. The main disadvantage of the proposed method is a poor flexibility of the acquisition duration, once out-of-synchronization occurs, data loss may be caused. Besides, the centralized reporting of mass data will easily lead to interference, and then result in data error. The time-asynchronous monitoring-sleeping method provides a high flexibility and reliability. The real-time data is obtained by immediately waking up the sensor node, and then the data is immediately reported in order to obtain the real-time determination from the system. This method requires a short monitoring-sleeping period of the wireless sensor, allowing timely response to the wake-up data packet transmitted by the data acquisitor and mobile terminal.
However, in the exiting time-asynchronous monitoring-sleeping method, the wireless sensor adopts the same monitoring durations for the data acquisitor and the mobile terminal, increasing the power consumption of wireless sensor within the monitoring duration and resulting in a large power consumption of the wireless sensor.